In a generally known method of measuring wear of a cutting tool during cutting work, acoustic emission (AE) is utilized as disclosed in Japanese Patent Laying-Open Gazette No. 138558/1982, for example. This AE method is adapted to detect with an HE-Sensor acoustic emission generated during the cutting work when a cutting tool breaks thereby to measure wear thereof. However, it is impossible to accurately detect only such acoustic emission since various noises are made on the jobsite where the actual cutting work is performed. Thus, the AE method is insufficient in accuracy.
Another conventional method is adapted to measure wear by measuring the cutting force caused during cutting work, as disclosed in Japanese Patent Laying-Open Gazette No. 5252/1980 or 218053/1987, for example. However, such cutting force varies with the configurations of the cutting positions of the workpieces etc. Thus, this method is not usable unless all the workpieces are regularly cut to have the same configuration.
In still another conventional method, a cutting tool is formed of a material containing a radioactive isotope such as radioactive cobalt, and a reduction of the radioactive isotope is measured through change its radioactivity, thereby to detect wear of the cutting tool. However, it is clear that such a method is not desirable, because the radiation may be harmful to the work environment.